Prestack depth migration

The data was migrated with source-receiver migration. The depth step was 10 m and 400 depth steps were computed in total. Figure  shows one SODCIG migrated with the correct velocity (left panel) and with 90% of the correct velocity (right panel). Obviously, with the correct velocity both primaries are well focused around zero subsurface offset, whereas the multiples are mapped to the negative subsurface offsets. With the slower velocities, the primaries are now mapped shallower, with downward moveout and toward the positive subsurface offsets. The multiples are still mapped to the negative subsurface offsets although they are somewhat closer to the zero subsurface offsets.